Answer:
13y + 12 + x
Explanation:
So your problem is 12y + 4 + x - 7y + 8 + 8y.
What you want to do first is line the variables up, so line the y's up, and then line the number without the variables, and then the x can go at the end.
So now you should have 12y - 7y + 8y + 4 + 8 + x
After that, you want to subtract 7y from 12y which gets you 5y.
So now it should look like 5y + 8y + 4 + 8 + x
After that, add 8y and 5y together to get 13y
13y + 4 + 8 +x
Add the 4 and the 8
13y + 12 + x
And that should be your answer